Thanks for reaching out. We are sorry for the trouble with Adobe Lightroom. We are here to help.
Did you import a large batch of images into Lightroom recently? What is the format of the images you work on? Are they JPEG or RAW?
Log on to Lightroom Web (https://lightroom.adobe.com) to check current Sync issues on the left part of the screen.
If there are any sync issues, click on them to know more, find the original for those images, and back them up safely before you empty the Sync issues from Lightroom Web. As long as there are Sync issues on the web, you might encounter trouble with syncing images and edits.
Let us know if this helps,